Isoscalar dipole transition as a probe for asymmetric clustering

Abstract

Background: The sharp $1^{-}$ resonances with enhanced isoscalar dipole transition strengths are observed in many light nuclei at relatively small excitation energies, but their nature was unclear. Purpose: We show those resonances can be attributed to the cluster states with asymmetric configurations such as $\alpha$+${}^{16}\mathrm{O}$. We explain why asymmetric cluster states are strongly excited by the isoscalar dipole transition. We also provide a theoretical prediction of the isoscalar dipole transitions in ${}^{20}\mathrm{Ne}$ and ${}^{44}\mathrm{Ti}$. Method: The transition matrix is analytically derived to clarify the excitation mechanism. The nuclear model calculations by Brink-Bloch wave function and antisymmetrized molecular dynamics are also performed to provide a theoretical prediction for ${}^{20}\mathrm{Ne}$ and ${}^{44}\mathrm{Ti}$. Results: It is shown that the transition matrix is as large as the Weisskopf estimate even though the ground state is an ideal shell model state. Furthermore, it is considerably amplified if the ground state has cluster correlation. The nuclear model calculations predict large transition matrix to the $\alpha$+${}^{16}\mathrm{O}$ and $\alpha$+${}^{40}\mathrm{Ca}$ cluster states comparable with or larger than the Weisskopf estimate. Conclusion: We conclude that the asymmetric cluster states are strongly excited by the isoscalar dipole transition. Combined with the isoscalar monopole transition that populates the $0^{+}$ cluster states, the isoscalar transitions are promising probe for asymmetric clusters.

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• Evidence for an alpha cluster condensed state in 16O(alpha,alpha') at 400 MeV
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• $\alpha +\alpha +t$ cluster structures and Hoyle-analogue states in ${}^{11}$B
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• Gas-like state of $\alpha$ clusters around ${}^{16}$O core in ${}^{24}$Mg

Cited by in corpus (31)

• Microscopic Clustering in Light Nuclei
• The Compression-Mode Giant Resonances and Nuclear Incompressibility
• Antisymmetrized molecular dynamics studies for exotic clustering phenomena in neutron-rich nuclei
• Testing microscopically derived descriptions of nuclear collectivity: Coulomb excitation of 22Mg
• Dipole oscillation modes in light $\alpha$-clustering nuclei
• Nonlocalized Clustering and Evolution of Cluster Structure in Nuclei
• Quantitative description of the ${}^{20}$Ne($p$,$p\alpha$)${}^{16}$O cross section as a means of probing the surface $\alpha$ amplitude
• ${}^{12}\mathbf{C}+{}^{12}\mathbf{C}$ Fusion ${\mathbf{S}}^{\ast }$-factor from a Full-microscopic Nuclear Model
• Real-time evolution method and its application to 3$\alpha$ cluster system
• Hoyle-analogue state in 13C studied with Antisymmetrized Molecular Dynamics
• Inversion doublets of reflection-asymmetric clustering in 28Si and their isoscalar monopole and dipole transitions
• Toroidal, compressive, and $E1$ properties of low-energy dipole modes in ${}^{10}$Be
• Structure and decay of the pygmy dipole resonance in 26Ne
• Re-examining the ${}^{26}$Mg($\alpha ,{\alpha }^{\prime }$)${}^{26}$Mg reaction - probing astrophysically important states in ${}^{26}$Mg
• Isoscalar dipole excitations in ${}^{16}$O
• Cluster and toroidal aspects of isoscalar dipole excitations in ${}^{12}$C
• 2$\alpha$+$t$ cluster structure in ${}^{11}$B
• First microscopic coupled-channel calculation of $\alpha$ inelastic cross sections on ${}^{16}$O
• Low-energy cluster vibrations in N = Z nuclei
• Analytical approach for the Quartet Condensation Model
• Role of Tensor Interaction as Salvation of Cluster Structure in ${}^{44}$Ti
• A variety of clustering in ${}^{18}$O
• Transition properties of low-lying states in ${}^{28}$Si probed via inelastic proton and alpha scattering
• Low-energy monopole strength in spherical and deformed nuclei : cluster and soft modes
• Monopole and dipole transitions of the cluster states of 18O
• Cluster correlation and nuclear vorticity in low-lying $1^{-}$ states of ${}^{24}$Mg
• alpha+28Si and 16O+16O molecular states, and their isoscalar monopole strengths
• Low-energy dipole excitation mode in ${}^{18}$O with antisymmetrized molecular dynamics
• Low-energy dipole excitation modes in ${}^{10}$Be
• Low-energy dipole excitations in ${}^{20}$O with antisymmetrized molecular dynamics
• Electromagnetic Excitations and Responses in Nuclei from First Principles